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Re: Problems with system locking
Posted by: Ananth Reddy ()
Date: June 13, 2006 09:59PM

Hi Guys,

We are experiencing exactly same problems in production.
I just posted my issue in other recent thread.

We are running MySQL in production for last 10 months and problem started coming now. We have 3-5 tables which are large; raging 30MM rows to 90MM rows in each
All of them or MyISAM tables

When it locks up it only lasts for less than a minute. and even 'SELECT 1' takes 30-60 seconds during this time. This results in application running out of threads and spits out errors to users. It is a web application and we are 24x7

We have instrumented some monitoring to see what is happening during that lock up time.

here is what we have noticed:

Not much IO from vmstats
Load is below average
One mysql thread is maxing out on CPU (25%) == we are suspecting that this thread is some housekeeping thread

System Config:
H/W: Dell 2CPU with internal disks with RAID 5 and hyper-threading
S/W: RedHat 4 with 2.4 kernel
MySQL 4.1.13


If that MySQL thread which is CPU bound is for flushing KEY CACHE dirty buffers, is there a solution to this? We have allocated 1GB for KEY CACHE. I am not sure if it takes that long to walk through 1GB memory. if that is infact what is happening, don't have a solution, then we are in for big trouble as far as scaling is concerned.

Is it possible to find what this one CPU bound mysql thread is doing by sending signal to process to dump trace?

Appreciate any help!

Thanks in Advance

ananth
PS Brian- if you want to talk about it over phone let me know

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Subject Views Written By Posted
Problems with system locking 7112 Brian O'Donnell 04/26/2006 05:37AM
Re: Problems with system locking 8358 Ingo Strüwing 04/27/2006 04:36AM
Re: Problems with system locking 3013 Brian O'Donnell 04/27/2006 07:41AM
Re: Problems with system locking 2550 Ingo Strüwing 05/02/2006 06:13AM
Re: Problems with system locking 2449 Brian O'Donnell 05/02/2006 07:49AM
Re: Problems with system locking 2080 Ingo Strüwing 05/02/2006 10:46AM
Re: Problems with system locking 1914 Brian O'Donnell 05/12/2006 04:10AM
Re: Problems with system locking 2048 Ingo Strüwing 05/15/2006 02:57AM
Re: Problems with system locking 2104 Brian O'Donnell 04/28/2006 03:23AM
Re: Problems with system locking 1913 Ingo Strüwing 05/02/2006 06:27AM
Re: Problems with system locking 2975 Ananth Reddy 06/13/2006 09:59PM
Re: Problems with system locking 1950 Ingo Strüwing 06/14/2006 08:04AM
Re: Problems with system locking 1996 Ananth Reddy 06/14/2006 10:22AM
Re: Problems with system locking 1969 Ingo Strüwing 06/15/2006 09:26AM
Re: Problems with system locking 2259 Ananth Reddy 06/15/2006 11:18AM
Re: Problems with system locking 2118 Ingo Strüwing 06/16/2006 03:18AM
Re: Problems with system locking 2008 Ananth Reddy 07/14/2006 03:52PM
Re: Problems with system locking 2012 Ingo Strüwing 07/31/2006 04:16AM
Re: Problems with system locking 2146 Ingo Strüwing 08/22/2006 11:34AM
Re: Problems with system locking 2143 Carsten Kosthorst 07/19/2006 04:07AM


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